Global Optimization in reTORT – Can quicker global optimization improve your workflow and your ROI?

Global Optimization in reTORT is an invaluable design tool. It’s different than any other global optimizer. It can also improve your workflow.

At an early stage in your design workflow, the E x H Global Opimizer yields an optimum design choice. And, it does it more quickly than others.

It’s a slightly different workflow but, it works well.

Recently, we ran a focus group about optimizers with a group of our Customers. Through this, we found that many did not use global optimization, at least not until the very end of their design project.

But why? These designers told us that some of the ray tracers they have used took hours or days to run Global Optimization. And then, they returned one hundred or more possible solutions. After that, the designer needed to sift through the solutions to find one or more they wanted to further refine.

That’s a huge time commitment. After all, your time is money. And, it can significantly stall progress on a lens design. But, that’s the way some ray tracers implement Global Optimization.

reTORT is an exception to this rule. In fact, Global Optimization in reTORT is extremely useful and will speed up your workflow.

reTORT‘s global optimizer returns one optimum result within your design constraints. On average, for a typical complex lens, it does this within a few minutes.

This feature allows comparison of alternative designs more quickly.

How reTORT works

reTORT employs evolutionary algorithms for its global optimizers. Specifically, they are based on a modified version of CMAES, or Covariance Matrix Adaptation Evolution Strategy. The E x H modifications to CMAES provide for speedy and accurate results.

Note the wizard provides easy access to the lens system parameters. This example is a gradient index lens employing binary mixtures to achieve the design objectives.

CMAES is capable of optimizing a very large search space with many variables. CMAES can easily generate new candidate lens designs from scratch with minimal oversight.

E x H found through its research that CMAES is much more efficient if you apply bounds. This may defy logic for some. For us, it has proven to work very well in our own designs.

You might ask, do bounds mean over-constraint? Not at all. All designs have some over-riding design objectives. These provide the basis for applying realistic bounds.

We hope to start bragging about our very useful status bar. You can see it below in an illustration of a global optimization. The status bar shows that 12,000 simulations were run and two can be seen taking from 65 to 85 milliseconds each.

The entire optimization took a total of 3.37 minutes.

Bounded versus Unbounded

Please remember, reTORT also offers a very efficient local optimizer based on the Damped Least-Squares (DLS) algorithm. DLS is run unbounded by default. This is in contrast to its global sister.

In our research, we found that bounded DLS algorithms tended to more easily fall into near optimums. In other words, they often take one of the first valleys they find. This is even though a better solution was available in the search space. It acted like one of our favorite little guys searching for an optimum below:

And so, reTORT’s DLS is unbounded based on our preferred workflow of first using bounded global optimization. Global optimization with CMAES is used to find a candidate design within mere minutes. Then, we use local optimization to test variations of that design and tune it even further. In that way, we can hone the design in less time. And with reTORT each iteration is faster than other tools.

But that is just our preferred workflow here at E x H. reTORT allows you to employ the workflow that you prefer. It does not lock you into one workflow or another. Instead, reTORT is extremely flexible.

The choice is always yours. A variety of Workflows are feasible due to the way global and local optimizers are deployed in reTORT. Even our optimization wizard allows quick and easy control of both from the same window.

A Variety of Workflows

Workflow does vary among designers, no matter which ray tracing tool they are using. In our recent focus groups among designers with experience with other ray tracers, we found that workflow preferences varied.

This does not mean one is right and the others wrong. reTORT is a valuable tool that leverages the designer’s creativity. But that creativity and the designer’s preference will still prevail in choosing a desired workflow.

We found three distinct workflows in our focus group.

Workflow Group 1

Some designers prefer always using Damped Least Squares (DLS). This is an extremely useful tool

Workflow Group 2

Others test various designs using DLS and then run global optimizers. This is the group that finds hundreds of possible optimum solutions in tools other than reTORT.

The reTORT global optimizer returns only the best solution. Those other tools, rank the range of alternative optimums, usually by merit function or cost scores. And finally, they focus on three or four finalists to refine. Ultimately, they finalize their design.

Quite a few in our focus group employed this method. They did see value and possible time savings when exposed to the third method using reTORT.

Workflow Group 3

This is the method usually used by E x H for Customer design projects. We run our global optimizer to zero in on one optimum solution within the design parameters. With very quick global optimization, we can run alternative designs quickly.

Any optimization can be saved by renaming it. In that way, we can easily return to a prior configuation. Then, we use DLS to search the local space to further improve that solution.

Is One Workflow Better than the Others?

There is no right or wrong here. The third method is the preference of our designers for most complex lens system design. But all methods are valid and up to the optical lens designer’s preference.

Workflow varies from designer to designer.

So, by design, reTORT does not force the designer into one particular workflow. reTORT allows you to follow the workflow just right for you and your task at hand.

The designer’s own creativity is the most valuable ingredient. This is why we’ve strived to make reTORT the most flexible tool on the market today.

But There’s More

You can easily have global and local optimizers configured at the same time. But they don’t necessarily run at the same time. You can switch from one to the other as you prefer. You can see this in the Optimizer Settings image above. Both methods are enabled at the same time.

If one of the three workflows above does not suit you, reTORT’s optimization wizard allow you to easily design your own workflow.

Even better, the wizard allows you to follow your creative instincts.

The reTORT wizards also give you immediate control over optimization settings, goals, and parameters. As you proceed with your design, your optimizer controls are right at hand for making quick tweaks.

You can also save multiple optimization configurations. The optimization wizard creates optimizations under the names “AutoCMAES” and “AutoDLS”. Save your optimizations by simply renaming them before running the wizard again. If you wish, come back later to revisit a prior configuration.

And the same power of our optimizers is equally available to you for including  gradient index lenses and metasurfaces in your optical lens system design. You are able to use the full power of reTORT using the most powerful and advanced lens features available to any designer today.

The reTORT Ray Tracer is truly a unique state-of-the-art tool for today’s optical lens designer.

Get Your Copy of v2.5.0 of the reTORT Ray Tracer

Current licensees – please use this link to update!

New Users – this download comes with a free trial license you can activate!

Please visit the site to download the most current version of reTORT at any time and update the version you are currently running.

For those who are not yet using our reTORT Ray Tracer, the same download link will provide you with a free two-week trial. Our license pricing and ordering list is the place to go to order.

You will be committing to the most technologically advanced ray tracer available today.

Coming in Future Posts

More on Tolerance Analysis, including our easy to use Tolerance Analysis Wizards. Download the latest version of the Tolerance Analysis User Manual.

And more on asymmetric aspheres. Look for a new release shortly.

About E x H, Inc.

E x H’s mission is to provide you with advanced optical system simulation tools. The result is tools that allow you to design optical systems that are smaller, lighter and faster. Watch our SWaP reduction use case tutorial for a taste of this.

Some of our solvers are licensed from Penn State University. PSU is one of the leading research institutions in the USA.

We have participated on multiple programs funded by DARPA that have allowed us to develop software on the leading edge of technology.

Outside of the optical space, this same reTORT Ray Tracer was used to fast prototype the transformational optics that proved the concept for Isotropic Systems’ high throughput, multi-beam satellite terminals (https://www.isotropicsystems.com/). 

On the business side, we have been backed by Gran Sasso Ventures, the same venture capitalists that funded collaboration software firm Compoze Software, now a part of Oracle [ORCL:NYSE], and multitouch technology inventor FingerWorks, the driver of touch screen technology and now a part of Apple [AAPL:NASDAQ]. E x H is at the forefront of transformation optics.For

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